Bucket locking mechanism

ABSTRACT

An arrangement for axially locking a turbomachinery blade in its associated disc slot includes a locking key, a keyway formed in the blade platform and a circumferential slot formed in the periphery of the disc. The locking key is recessed in the platform keyway to permit insertion of the blade and is then dropped into the disc slot and rotated 90* to lock the blade to the disc.

United States Patent Cardin et al. 1 Sept. 9, 1975 [54] BUCKET LOCKING MECHANISM 2,949,278 8/l960 McCormick 416/220 3,l98,485 8 1965 M l h k 416 220 [75] Inventors: Robert A. Cardin, Schenectady; c enc u Kenneth P. Zeman, Burnt Hills, both FOREIGN PATENTS OR APPLICATIONS Of 313,027 4/!956 Switzerland 416/220 {73] Assignee: General Electric Company,

Schenectady, Primary ExaminerEverette A. Powell, Jr.

Attorney, Agent, or FirmErwin F. Berrier, Jr, [22] Filed: Nov. 27, 1974 [21] Appl No: 527,586 [57] ABSTRACT An arrangement for axially locking a turbomachinery [52] U S Cl, 416/220 blade in its associated disc slot includes a locking key, [51] Int. Cl, v v F011) 5/32 a keyway formed in the blade platform and a circum- (581 Field of S ar h 416/193 220 ferential slot formed in the periphery of the disc. The locking key is recessed in the platform keyway to per [56] i References Cit d mit insertion of the blade and is then dropped into the diSC S10 and rotated 90 to lock the blade to the disc,

1861408 l/l959 Kolb ct al. 416/193 5 Claims, 9 Drawing Figures PATENTEU SE? 9 I975 SHEET 1 BF 2 PATENTEDSEP ems 3,904,317

SHEET 2 0f 2 BUCKET LOCKING MECHANISM This invention relates to turbomachines and, more particularly, to improved means for axially retaining a blade or bucket in a turbomachinery rotor or disc.

BACKGROUND OF THE INVENTION Blade locks which have been heretofore proposed for use in axially locking a blade within a generally axially extending rotor or disc slot have usually included a member which extends axially across the disc adjacent the blade or bucket root. A great number of these locking devices have included one or more tabs that are bent after assembly to axially lock the rotor in its slot. Such arrangements are, however, undesirable in that the axial forces required to retain the blade in its slot are usually reacted by a member which has been bent during assembly. In addition, the bent tab usually has some residual strain which may result in spring-back of the bent tab and axial looseness of the blade.

Another solution has employed the use of both a spacer and a locking clip so that the tab that is bent at assembly retains only the spacer. While this solution overcomes the problem of reacting axial blade forces through a tab that is bent at assembly and the problem of tab spring-back. it does require two parts, access to at least one side of the turbomachinery disc, and the bending at assembly of one tab to retain the spacer.

A further solution to axially locking a turbine blade is shown in US. Pat. No. 2,867,408, issued Jan. 6, 1959, and involves a locking key that is engaged in a rotor slot and a platform slot. To lock the array of blades in place using the arrangement shown in the aforementioned patent. however, the last key must be expanded by peening so as to fill the slots formed in adjacent blade platforms. Moreover, with such an arrangement, to remove and replace one blade. all blades would have to be removed.

A primary object of this invention, then, is to provide a blade retainer or lock that does not require the bending of any tabs at assembly; that permits the blade to be locked to the disc without access to either side of the disc; and that enables removal and replacement of a single blade.

SUMMARY OF THE INVENTION Briefly stated, the present invention provides a locking key which includes a rectangular block portion with a generally cylindrical stem extending therefrom. A keyway is formed in the platform portion of the turbomachinery blade to receive the locking key from the underside of the platform, with the block portion recessed into a slot and the stem projecting through an opening formed in the platform. A keyway slot is formed in outer circumferential surface of the disc in a position under the platform keyway. The block portion of the key has a length dimension greater than its width dimension. The axial length of the platform slot is sized to correspond to the smaller width dimension of the locking key block, whereas the axial length of the disc keyway slot is sized to correspond to the longer length dimension of the locking key block. In this manner. the locking key may be dropped radially into the disc keyway slot and rotated 90to axially lock the blade to the disc.

Suitable means such as a screw driver slot may be provided at the distal end of the locking key stem to facilitate rotating the locking key into and out of its locked position.

The stem may be conveniently staked or otherwise suitable secured to the platform to prevent the locking key from rotating out of its locked position during operation of the bladed turbomachinery disc.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of this invention, it is believed that the invention will be better understood upon reading the following description of the preferred embodiment in conjunc tion with the accompanying drawings, Wherein:

FIG. 1 is a partial perspective view showing an exemplary bladed turbomachinery disc employing the blade locking means of this invention;

FIG. 2 is an enlarged perspective view showing the locking key of this invention;

FIG. 3 is an enlarged partial cross-sectional view taken along lines 33 of FIG. 1;

FIG. 4 is a view like that of FIG. 3 showing the locking key of FIG. 2 in its position enabling insertion of the blades into its associated disc slot;

FIG. 5 is an enlarged fragmentary plan view taken along lines 5-5 of FIG. 3 and showing the locking key of FIG. 2 in its locked position;

FIG. 6 is a view like FIG. 5 taken on lines 66 of FIG. 4 and showing the locking key of FIG. 2 in its unlocked position;

FIG. 7 is a partial perspective view like that of FIG. I. but with the blade removed from its disc slot;

FIG. 8 is an enlarged fragmentary cross-sectional view taken along lines 8-8 of FIG. 4 and showing the locking key of FIG. 2 in its unlocked position; and

FIG. 9 is a view taken on lines 99 of FIG. 3 showing the locking key of FIG. 2 in its locked position.

DETAILED DESCRIPTION OF THE INVENTION With reference now to the drawings and particularly to FIG. 1, a bladed turbomachinery rotor or disc has been shown generally at 10 as comprising a rotatable annular disc 12 supporting at its periphery a plurality of radially extending blades or buckets I4. The blades 14 include an airfoil portion 16, a platform portion I8 and a root portion 20. The disc I2 is formed with a slot 22 for each blade I4 which extends generally axially across the disc 12 at its periphery and is shaped, in cooperation with the blade root 22, to axially receive the blade root and to radially lock the blade I4 to the disc against centrifugal forces.

As shown in FIG. I, the blade platforms extend over the outer circumferential surface 23 of the disc I2 so as to form the inner boundary of fluid flow across the blade airfoils 16.

The means of this invention for axially locking the blade root 20 in the disc slot 22 include a locking key 24 and associated keyways 26 and 28 formed, respectively, in the blade platform and the outer peripherial surface 23 of the disc I2.

With reference now to FIG. 2 the locking key 24 has been shown as including a block portion 30 and a stem portion 32. The block portion 30 is generally rectangular in shape and has a radial thickness 1, a width w, and a length l. The stem portion 32 is preferably cylindrical and extends normally from the central portion of the radially outwardly facing surface of the block 30. The

outer radial end 34 of the stem 32 is formed with a screw driver slot or other suitable means 35 to enable rotation of the key 24 into its locked position as will be hereinafter described.

With reference now to FIGS. 3, 4 and 5, the platform keyway 26 includes a slot 36 formed in the radially inner side of the platform 18 and an opening 38 communicating with the slot 36 and extending radially through the blade platform 18. As best shown in FIG. 5 the axial width W of the platform slot 36 is sized to receive the width dimension w of the locking key block 30 and has a radial height sized to receive the thickness dimension t of the key block 30 in noninterfering relationship with the disc periphery 23, with the stem por tion 32 extending through the keyway opening 38 as shown in FIG. 4.

The disc keyway 28 takes the form of a circumferential slot which has an axial length L and radial height T, as shown in FIG. 3, which are sized, respectively, to correspond to the length dimension 1 and the thickness dimension of the block 30.

The slot 28 is located axially so that when the blade 14 and root portion are inserted in the disc slot 22, the slot 28 will be aligned with the keyway 26 formed in the blade platform 18.

These. operation and function of the present invention are as follows. The locking key 24 is inserted into the platform keyway 26 shown in FIGS. 4 and 6, with the block portion received within platform slot 36 and the stem portion 32 projecting through platform opening 38. The blade I4 is then axially inserted into its re spective rotor slot 22.

With the blade positioned within its rotor slot 22 as shown in FIG. 4, the locking key 24 is dropped radially inward so that the block portion 30 engages the disc keyway 28. The locking key 24 is then rotated 90, using slot means 35. from the unlocked position of FIGS. 6 and 8 to the locked position of FIGS. 5 and 9, wherein the length dimension I of the block 30 is oriented in an axial direction.

Opposed corners of the block 30 are appropriately contoured. as at in FIGS. 2, 6 and 8, so as to permit the key 24 to be rotated or cammed 90into locking en gagement with the slot 28.

Since the axial length or W dimension of the platform slot is smaller than the axial length or L dimension of the rotor slot. the locking key is radially retained in its locked position of FIGS. 3, 5 and by abutment of the radially outer face of block 30 with the radially inner side of the blade platform I8. At the same time. axial movement of the blade is prevented by abutment of the locking key stem 32 with the walls of platform opening 38 and by abutment of the block 30 with the disc slot 28.

As best shown in FIGS. 1 and 3, the stem 32 is preferably sized, for aerodynamic reasons, so that when the locking key 24 is engaged in its locked position in the disc slot 28, the distal or outer radial end 34 will be generally flush with the outer surface of the platform.

During operation of the turbomaehine, to prevent the locking key from rotating from its locked position of FIGS. 5 and 9 to its unlocked position of FIGS. 6 and 8, the distal end of the stem 32 may be staked to the platform 18 as shown in FIG. 5 or otherwise suitably secured. In this regard, suitable slots 42 may be provided in the platform, adjacent the keyway opening 38 to facilitate such staking operation. At the time of staking the slot 35 of the stem 32 will be at right angle to the slots 42 to assure a positive locking of the turbine blade 14 and the disc I2.

To remove a blade from the disc 12. the above procedure is reversed. The locking key is rotated to its un locked position of FIG. 8, moved radially outwardly, out of engagement with disc slot 28 and into platform slot 36 of the keyway 26, and the turbine blade 14 is slid axially out of engagement with the disc dovetail slot 22. Alternatively, and depending on the relative size and strength of the stem portion 32 and the blade platform 18, the stem portion may be sheared from the block portion 30 by applying a sharp blow to an axial face of the root portion 20.

From the foregoing, it will be appreciated that the present invention provides means for axially locking a blade or bucket to a turbomachinery disc which does not require the bending of any retaining tabs at assembly and which permits a single blade to be removed and replaced without disturbing adjacent blades.

While a preferred embodiment of the present invention has been depicted and described, it will be appreciated by those skilled in the art that many modifications, substitutions and changes may be made thereto without departing from the inventions fundamental theme.

What is claimed is:

1. In a turbomachine of the type including a rotatable disc formed with at least one slot extending generally axially of said disc at its periphery, a blade extending generally radially from said disc and having a root portion engaged in said axial slot and a platform portion, extending over a portion of the periphery of said disc, said axial slot and said root portion sized and formed to abut and radially lock the blade to the disc against centrifugal forces. means for axially retaining said blade root in said axial slot comprising:

a locking key having a block portion and an elongated stern portion extending therefrom and terminating at a distal end;

said block portion having a thickness defined by radially inwardly and outwardly facing surfaces, a width, and a length of greater extent than said width, said stern extending normally from a central position ofsaid radially outwardly facing block surface;

said platform portion formed with a circumferentially extending slot in its radially inner side, said platform slot having an axial width sized to receive the width dimension of said block in close fitting relationship thereto and having a radial height sized to receive said block in noninterfering relation with said disc, a radial opening formed through said platform portion and communicating with said platform groove for receiving said stem portion, in close fitting relationship therewith, when said block is engaged in said platform groove and for providing access to the distal end of said stem;

a circumferential slot formed in the periphery of said disc adjacent said axial slot, said disc circumferential slot having an axial length sized to receive the length dimension of said block in close fitting relationship therewith, said disc circumferential slot located and having a radial depth such that when said blade is inserted into said axial disc slot, said locking block may be dropped radially out of engagement with said platform slot and into engagement with said disc peripherial slot and then roin that said block is generally rectangular and includes diametrically opposed arcuate surfaces to permit rotation into its locking position.

5. The combination of claim 1 further characterized in that said stem portion is staked to said platform portion to prevent said block from rotating out of its locked position.

* a: k a: 

1. In a turbomachine of the type including a rotatable disc formed with at least one slot extending generally axially of said disc at its periphery, a blade extending generally radially from said disc and having a root portion engaged in said axial slot and a platform portion, extending over a portion of the periphery of said disc, said axial slot and said root portion sized and formed to abut and radially lock the blade to the disc against centrifugal forces, means for axially retaining said blade root in said axial slot comprising: a locking key having a block portion and an elongated stem portion extending therefrom and terminating at a distal end; said block portion having a thickness defined by radially inwardly and outwardly facing surfaces, a width, and a length of greater extent than said width, said stem extending normally from a central position of said radially outwardly facing block surface; said platform portion formed with a circumferentially extending slot in its radially inner side, said platform slot having an axial width sized to receive the width dimension of said block in close fitting relationship thereto and having a radial height sized to receive said block in noninterfering relation with said disc, a radial opening formed through said platform portion and communicating with said platform groove for receiving said stem portion, in close fitting relationship therewith, when said block is engaged in said platform groove and for providing access to the distal end of said stem; a circumferential slot formed in the periphery of said disc adjacent said axial slot, said disc circumferential slot having an axial length sized to receive the length dimension of said block in close fitting relationship therewith, said disc circumferential slot located and having a radial depth such that when said blade is inserted into said axial disc slot, said locking block may be dropped radially out of engagement with said platform slot and into engagement with said disc peripherial slot and then rotated to axially lock the blade in the axial disc slot.
 2. the combination of claim 1 further characterized in that the distal end of said stem portion includes means to facilitate rotation of said locking key into and out of its locking position.
 3. The combination of claim 1 further characterized in that said stem portion is cylindrical.
 4. The combination of claim 1 further characterized in that said block is generally rectangular and includes diametrically opposed arcuate surfaces to permit rotation into its locking position.
 5. The combination of claim 1 further characterized in that said stem portion is staked to said platform portion to prevent said block from rotating out of its locked position. 